The X-ray source population The X-ray source population of M 31 and M 33 of M 31 and M 33

Wolfgang PietschMax Planck Institut für extraterrestrische Physik

OutlineOutline

• Introduction to X-ray source population in galaxy fields

• X-ray source population of M 33 field

• X-ray source population of the Andromeda galaxy M 31 field

• Outlook

Talk restricted mainly to XMM-Newton resultsChandra results presented by B. WilliamsLuminosity functions M. Gilfanov and others

Why observe Nearby GalaxiesWhy observe Nearby Galaxies

• Nearby examples of early and late types of galaxies

• “Same” distance to all sources in a galaxy • Different source classes resolved• Better understanding of population of the

Milky Way• Understanding of unresolved emission from

distant galaxies

Introduction: X-ray sources in nearby Introduction: X-ray sources in nearby galaxy fieldsgalaxy fields

– Sources within galaxy (all approximately at same distance)• X-ray binaries (XRBs)

– Low mass XRBs (?dips with orbital period, bursts, ...) – High mass XRBs (?eclipses with orb. period, pulsations, optical id,...)– Bright transients

• Supersoft X-ray sources– Classical SSS as known from Magellanic Clouds– Optical novae (dominant class of SSS in M 31)

• Supernova remnants– Thermal remnants– Plerions (PWN)

• Nuclear source • Ultraluminous X-ray sources• Diffuse emission in disk and halo

– Foreground stars– Galaxies, galaxy clusters and AGN in background

408 X–ray sources

X-ray properties

Correlation with catalogues from other wavelength

Optical identification

Identify foreground and background sources

Characterization of X-ray source population of M 33

XMM-Newton survey of the Local GroupXMM-Newton survey of the Local Group galaxy M 33 galaxy M 33 W. Pietsch, Z. Misanovic, F. Haberl,

D. Hatzidimitriou, M. Ehle, G. Trinchieri 2004, A&A 426, 11

Hardness ratio plots of M 33 sourcesHardness ratio plots of M 33 sourcesHRi = (Bi+1 – Bi)/ (Bi+1 + Bi) B1: 0.2-0.5 keV

B2: 0.5-1.0 keV B3: 1.0-2.0 keV B4: 2.0-4.5 keV B5: 4.5- 12 keV

fg-star

AGN

SSS

SNR

XRB

Hardness ratio plots of M 33 sourcesHardness ratio plots of M 33 sourcesHRi = (Bi+1 – Bi)/ (Bi+1 + Bi) B1: 0.2-0.5 keV

B2: 0.5-1.0 keV B3: 1.0-2.0 keV B4: 2.0-4.5 keV B5: 4.5- 12 keV

fg-star

AGN

SSS

SNR

XRB

Hardness ratio plots of M 33 sourcesHardness ratio plots of M 33 sourcesHRi = (Bi+1 – Bi)/ (Bi+1 + Bi) B1: 0.2-0.5 keV

B2: 0.5-1.0 keV B3: 1.0-2.0 keV B4: 2.0-4.5 keV B5: 4.5- 12 keV

fg-star

AGN

SSS

SNR

XRB

X-ray sources in M 33 field: X-ray sources in M 33 field: identification and classificationidentification and classification

identified classified• foreground stars 5 30• AGN 12• Galaxies 1 1

• SSS 5• SNR 21 (+2) 23 (-2)

(Ghavamian et al. 2005, AJ 130, 539)• XRB 2• Hard 267

Using X-ray hardness ratio criteria, optical correlation with USNO-B1, catalogues at different wavelengths, SIMBAD, NED

Variability of M 33 sources between Variability of M 33 sources between XMM-Newton pointingsXMM-Newton pointings

Misanovic, Pietsch, Haberl, Ehle, Hatzidimitriou, Trinchieri 2006, A&A 448, 1247

• Analysis of individual observations

• 39 new sources

• improved positions and time

variability

• 8 new XRB candidates

• SNR luminosity function

M 33 zoom in

M33 X-7

[PMH2004] 47

Einstein + ROSAT observations: 3.45 d period 0.31 s pulsation?

Peres et al. 1989, ApJ 336, 140; Dubus et al. 1999, MNRAS 302, 731

Eclipsing X-ray binary M33 X-7Eclipsing X-ray binary M33 X-7

On state Eclipse On state

XMM-Newton EPIC Chandra ACIS I

0.5-4.5 keV images

Eclipsing X-ray binary M33 X-7Eclipsing X-ray binary M33 X-7Pietsch et al. 2004, A&A 413,

879

Optical identification

Star with V 18.9 mag with 3.45 d variability

DIRECT image by B. Mochejska

Green circle: ROSAT error box Haberl & Pietsch 2001

Yellow circle: Chandra error box

Insert HST image

10“ x 10“

Pietsch et al. 2006, ApJ 646, 420

Eclipsing X-ray binary M33 X-7Eclipsing X-ray binary M33 X-7Pietsch et al. 2004

XMM-Newton EPIC + Chandra ACIS-I

Optical V and B-V light curve

re-analysis of DIRECT data by

B. Mochejska

folded modulo 3.45d period Dubus et al. 1999

Improved binary ephemeris

Eclipsing X-ray binary M33 X-7Eclipsing X-ray binary M33 X-7Pietsch et al. 2004, A&A 413, 879

Best fitting spectral models:Absorbed bremsstrahlung or disk blackbody

Eclipsing X-ray binary M33 X-7Eclipsing X-ray binary M33 X-7

First eclipsing black hole (high mass) X-ray binary ?

ChASeM33 light curve of X-7ChASeM33 light curve of X-7 Pietsch et al. 2006, ApJ 646, 420

Gemini North radial velocity curve: 15.65 Msun black hole with 70 M sun companionOrosz et al. 2007, ATel 977, Nature 2007, accepted

ChASeM33 light curve of ChASeM33 light curve of [PMH2004] 47[PMH2004] 47

Pietsch et al. 2006, ATel 905

2nd eclipsingHMXB in M33

Orbital period1.73245 d

Similar to LMC X-4 orHer X-1

The Andromeda The Andromeda Galaxy M 31Galaxy M 31W. Pietsch, M. Freyberg, F. Haberl et.al. 2004, A&A 434, 483

• Similar analysis to M 33 based on archival data

• 856 sources in fields

• Hardness ratio and time variability

• classification and identification

M 31 centreM 31 centreAll EPIC mosaic (~100 ks)

• SNRs, SSSs

• foreground stars

• diffuse emission

• Many LMXBs

• Galaxtic center sources not fully resolved

Movie of centre area by blinking four observationswith separation of half a year plus one 2.5 year later

X-ray sources in M 31 field: X-ray sources in M 31 field: identification and classificationidentification and classification

identified classified• foreground stars 6 90• AGN 1 36• Galaxies 1 • Galaxy clusters 1 1

• SSS 18• SNR 21 23• Globular clusters 27 10• XRB 7 9• Hard 567

Summary catalogueSummary catalogue

• HR2-HR1 diagram important to select SSS, thermal SNRs and foreground stars

• fx/fopt separate SNRs and foreground stars

• Hard X-ray spectra very important for classification: should separate

– XRBs

– Active nuclei

– Plerions

• Individual papers on bright sources (Osborne et al, Barnard et al., Trudolyubov et al., Mangano et al., …)

• Time variability studies to identify XRBs

W. Pietsch & F. Haberl 2005, A&A 430, L45

• search for X-ray bursts in GC candidates from catalogue paper

• 37 sources in fields

• most GC sources in center field that got longest exposure

• two burst sources detected in X-ray faint GCs, neutron star LMXBs

XMM-Newton detection of type I XMM-Newton detection of type I X-ray bursts in M 31X-ray bursts in M 31

X-ray burster [PFH2005] 253 X-ray burster [PFH2005] 253 in the GC [WSB85] S5 15in the GC [WSB85] S5 15

Observation c4 Jan 7, 2002

X-ray burster [PFH2005] 253 X-ray burster [PFH2005] 253 in the GC [WSB85] S5 15in the GC [WSB85] S5 15

Rise time < 10 s Total 50 ctsMaximum duration < 20 s Max. rate 1.4±0.4ct/s Decay to backgr. ~150 s corresponds to 3.8 1038erg/sQuiescent luminosity ~5 1036erg/s (Eddington limit for H-poor matter)

Pietsch, Fliri, Freyberg, Greiner, Haberl, Riffeser, Sala 2005, A&A 442, 879

• search for optical nova correlations in XMM- Newton, Chandra and ROSAT catalogs and archival observations

• 21 X-ray counterparts in M 31 and 2 in M 33

• novae dominant class of supersoft X-ray sources in M 31 center

• determine masses of ejecta and burned mass from lightcurve

Optical novae: the major class of supersoft Optical novae: the major class of supersoft X-ray sources in M 31X-ray sources in M 31

10 arcmin

Chandra HRC nova detections 2004/5Chandra HRC nova detections 2004/5 Pietsch et al. 2007, A&A 465, 375Pietsch et al. 2007, A&A 465, 375

Nova SSS light curves (<250 d)

More than 30% of optical novae show SSS state

Summary optical novaeSummary optical novae• 30 to 50 optical novae per year in M 31 (~half in bulge area)• Novae established as major class of SSS in M 31 center• Monitoring of bulge area gives light curves of many novae simultaneously inone

XMM-Newton/Chandra field (Galactic novae can only be monitored one by one, i.e. is much less efficient)

• Spectra can be modeled by BB spectra (T <70 eV)• Novae as SSS best detectable with XMM-Newton EPIC pn, Chandra HRC I and

ACIS S• SSS state of novae may start within 50 days after optical outburst • X-ray outburst may last only 2-3 months, but three of the novae still bright nine

years after optical outburst (similar to GQ Mus and Nova LMC 1995)• several novae missed in optical and X-ray searches• Number of X-ray detected optical novae much higher than previously estimated

(>30%)• X-ray light curves give estimates for ejected hydrogen mass for optical novae as

well as burned mass and mass of White Dwarf by comparing with models, that include chemical composition

??? Recurrent novae precursor of type Ia supernovae ???

SNR identifications by comparison with Local SNR identifications by comparison with Local Group survey images by Massey et al. (I)Group survey images by Massey et al. (I)

M 31 examples Halpha and [SII] images of SNRs and candidates

SNR identifications by comparison with Local SNR identifications by comparison with Local Group survey images by Massey et al. (II)Group survey images by Massey et al. (II)

M 31 examples Halpha and [SII] images of SNRs and candidates

Stiele, Pietsch, Haberl, Freyberg 2007, A&A, in preparation

• 39 new sources in individual pointings

• Determine time variability between M 31 center pointings half a year apart

• Check classification of SNRs

• Classify new XRB candidate by time variability

Time variability of X-ray sources in the Time variability of X-ray sources in the M 31 centre field (2000 – 2004)M 31 centre field (2000 – 2004)

1035 1036 1037 1038 erg/s

Time variability versus hardness ratiosTime variability versus hardness ratios

0.2-0.5 keV

0.5-1.0 keV

1.0-2.0 keV

Variable X-ray sources in the M 31 centre

On-going M 31 On-going M 31 programs involving programs involving

XMM-NewtonXMM-Newton

- M 31 raster survey AO5 and AO6 see talk by H. Stiele

- first colour image- about 2000 sources- identification - population study

- Monitoring of M 31 centre XMM-Newton/Chandra

- AO5 and AO6- monitoring optical novae as SSS sources

SummarySummary• XMM-Newton observations of M 31 and M 33 revealed

many exciting results• Demonstrated that X-ray sources in Local Group galaxies

can be well classified• Important: long (>50 ks) uninterrupted observations per

field• Separation of different source populations by hardness

ratios and time variability very efficient• SSS observations of optical novae demonstrate that

specific source classes can be more homogeneously investigated in galaxies outside Milky Way

• Wealth of sources with good positions (including Chandra source catalogues) for follow-up in other wavelength regimes (HMXBs, SNRs, SSS, transients versus foreground stars and sources in background)

What XMM-Newton should do What XMM-Newton should do next in Nearby Galaxy fieldnext in Nearby Galaxy field

• Survey full area of SMC (see Frank Haberl’s talk)• Survey systematically large part of LMC• Deeper observations of M 33 (>100 ks exposures)

Chandra VLP results show potential for finding XRB periods • Continue monitoring of M 31 centre for optical

novae and other transients2.6x2.6 dgr daily optical survey of M 31 in 2008 with PANSTARRS

Comparison X-ray source populations to the Milky Way and other nearby galaxies